1. Field of the Invention
The present invention relates to a non-specific reaction suppressor for immunoassays. More specifically, the present invention relates to secondary and tertiary amines which, when added to an immunoassay, improve the accuracy and reliability of the quantitative determination of the extent of immunoreactant-complementary immunoreactant interaction by significantly reducing or eliminating non-specific interactions.
2. Discussion of the Background
Immunoassays are techniques for the detection and/or quantitation of antigens, antibodies, etc. and are well known in the art. Immunoassays are described in the Handbook of Experimental Immunology, Vols. 1-4, Blackwell Scientific, incorporated herein by reference. U.S. Patents describing immunoassays include U.S. Pat. Nos. 4,203,724, 4,590,156, 4,716,123, 4,772,550, 4,851,329, 4,960,692 and 5,100,805, all incorporated herein by reference.
Non-labeled immunoassays have limited sensitivity since large antigen-antibody complexes must be formed for their detection. Examples of non-labeled reagent assays include immunoprecipitation methods, agglutination methods and light scattering techniques. Labeled reagent immunoassays include reagents labeled with radioisotopes, fluorophores, etc.
Immunoassays are broadly divided into two general groups: reagent observed and analyte observed (see Ekins, R., Immunoassay for the Eighties, University Press, Baltimore, Md, 1981, incorporated herein by reference). In reagent observed immunoassays an analyte to be detected and a complementary immunoreactive species present in excess are brought together. Examples include sandwich assays, etc. In analyte observed immunoassays, the analyte to be determined is labeled and is present in excess. Radioimmunoassays (RIA) represent a form of this type of assay wherein the analyte is labeled with a radioisotope.
Enzyme immunoassays (EIAs) measure the immunoreactant-complementary immunoreactant (i.e., antigen-antibody) reaction using enzyme reaction measurements. Recently EIAs have experienced rapid growth in the clinical laboratory due, in part, to the lack of a need for radioisotopes. Current EIA methods include homogeneous assays which do not include a separation step (because signal modulation occurs following immunoreactant-complementary immunoreactant reaction).
While immunoassays are generally classified on the basis of which immunoreactant (antigen or antibody) is determined, which reactant is labeled, whether competitive or non-competitive methods are used and which method of separation of bound and free reactants (if any) is used, all immunoassays rely, eventually, upon the formation of at least one immunoreactant-complementary immunoreactant complex.
Immunoassays are designed to detect, monitor and/or quantitate this complex formation and, preferably, provide a means by which the amount of a target species in a given sample is determined. To effect complex formation, generally an immunoreactant is bound to the surface of a bead, plate, etc., which surface is then brought into contact with a solution of complementary immunoreactant. The immobilization of immunoreactants on solid supports is well known in the art and described in, e.g., Immobilized Affinity Ligand Techniques, by G. T. Hermanson, et al, 1992, and U.S. Pat. Nos. 4,203,724, 4,716,123, 4,772,550, 4,851,329, 4,960,692 and 5,100,805, all incorporated herein by reference.
While the sensitivity of immunoassays has made them popular techniques in the determination of analytes, immunoassays, in addition to the desired immunoreactant-complementary immunoreactant reaction described above, undergo non-specific reactions which interfere with the determination of an analyte's presence and/or concentration. These non-specific reactions are well known in the art and are described in, e.g., L. M. Boscato et al, Clin. Chem., 32/8, 1986; H. C. Vaidya et al, Clin. Chem., 38/9, 1992; and C. Chang et al, Clin. Chem., 33/6, 1987, all incorporated herein by reference. Non-specific reactions may arise from non-analyte antibody-binding substances present in the sample being tested, from the interaction of labeled or non-labeled analyte with the solid immunoreactant support, etc. In the past, bovine serum albumin, etc. has been used to minimize non-specific interactions. However, non-specific reactions remain a problem in immunoassay techniques.